Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$215.78	8.502%	$234.1256	$234.13	$234.15	$234.10
Purchase #2	$39.88	6.215%	$42.3585	$42.36	$42.35	$42.40
Purchase #3	$134.57	8.797%	$146.4081	$146.41	$146.40	$146.40
Purchase #4	$30.94	13.345%	$35.0689	$35.07	$35.05	$35.10
Purchase #5	$76.47	11.712%	$85.4262	$85.43	$85.45	$85.40
Purchase #6	$199.64	5.829%	$211.277	$211.28	$211.30	$211.30
Purchase #7	$220.94	6.151%	$234.53	$234.53	$234.55	$234.50
7 purchase totals =	$918.22		$989.1943	$989.21	$989.25	$989.20